Second harmonic generation light quantifies the ratio of type III to total (I + III) collagen in a bundle of collagen fiber
Shukei Sugita, Takuya Suzumura, Akinobu Nakamura, Shinya Tsukiji, Yoshihiro Ujihara, Masanori Nakamura
Abstract
Abstract The ratio of type III to type I collagen is important for properly maintaining functions of organs and cells. We propose a method to quantify the ratio of type III to total (type I + III) collagen ( λ III ) in a given collagen fiber bundle using second harmonic generation (SHG) light. First, the relationship between SHG light intensity and the λ III of collagen gels was examined, and the slope ( k 1 ) and SHG light intensity at 0% type III collagen ( k 2 ) were determined. Second, the SHG light intensity of a 100% type I collagen fiber bundle and its diameter ( D ) were measured, and the slope ( k 3 ) of the relationship was determined. The λ III in a collagen fiber bundle was estimated from these constants ( k 1-3 ) and SHG light intensity. We applied this method to collagen fiber bundles isolated from the media and adventitia of porcine thoracic aortas, and obtained λ III = 84.7% ± 13.8% and λ III = 17.5% ± 15.2%, respectively. These values concurred with those obtained with a typical quantification method using sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The findings demonstrated that the method proposed is useful to quantify the ratio of type III to total collagen in a collagen fiber bundle.